Many material handling applications in shipping and industry employ lifting devices such as boom type or overhead travelling type cranes. These cranes utilize a hoisting mechanism attached to a hook assembly to which the load to be lifted is secured. Commonly the load is engaged to the hook assembly by means of a load ring and chain or cable sling assembly. After the load is hoisted and transported to its destination, the load ring is manually removed from the hook assembly.
The procedure of manual load ring removal, in addition to requiring manpower, presents problems where the load must be deposited in dangerous or inaccessible locations.
Many hooked mechanisms have been devised to provide for automatic removal of the load ring upon deposit. These mechanisms eject the load ring by force provided, for example, by an electrically operated solenoid. One spring operated mechanism permits pivoting or opening of the hook jaw or jaws allowing the ring to fall. U.S. Pat. No. 2,582,990 discloses an automatic parachute hook ground release designed to eject the load supporting link when the load is removed. Loading permits a piston to slowly fall out of the locking position while the parachute and load are falling such that when the parachute hits the ground and unloads, the link is ejected by spring action. The falling piston is an unacceptable condition for hooks used in industrial settings. All parts of a hook assembly must remain associated. U.S. Pat. No. 3,539,217 discloses a self-releasing cargo hook with a rotating jaw for opening upon release of load to enable the hook to be drawn away from the load ring. The problem with a rotating jaw mechanism is that the entire load is carried by the pin about which the jaw rotates. The shear strength of the pin is a significant limitation. U.S. Pat. No. 3,918,758 relates to a snap hook having a pivotally mounted release lever that can be manually pulled by a lanyard arranged to lift the load ring from the hook opening once the load has been removed.
It is a purpose of applicant's invention to provide ejection by an internal latching and release mechanism which is completely independent of the load carrying portion of the hook, thus preventing any malfunction or failure of any moving parts or connections thereof from interfering with the safe load carrying capability of the hook. It is a further advantage that no moving parts or connections thereof support any load in excess of those required to facilitate load ring ejection. According to one embodiment, the automatic load ring ejection is completely self-contained requiring no external forces or electrical connections. In this embodiment, mere release of the loading results in ejection of the load ring. In yet another embodiment of the invention a mechanical latch is arranged to be released manually or by a small electrical solenoid. The latch holds off the ejecting function until release. The load must still be removed to permit ejection of the load ring whether or not the mechanical latch has been released.
This application is directed to a device that has the advantages of the above discussed patented devices but avoids the drawbacks of each. It is an advantage of this invention to provide a self-releasing hook that remains assembled and has no parts capable of falling away. It is an advantage of this invention to provide a self-releasing hook that does not have a rotating jaw. It is yet another advantage of this invention to provide a self-releasing cargo hook that can be actuated by pulling of a release latch and/or unloading. Springs within the hooks supply the ejection force.